Sheep Milk: Milk composition

New Zealand sheep milk contains higher levels of health-beneficial lipids and fatty acids than European sheep milk or cow milk and microbiological testing shows that New Zealand sheep milk is safe.

Although differences in milk composition between species have been known for a long time, prior to the start of this research programme there was no data available on the detailed composition of New Zealand sheep milk. We did not know:

• Whether the composition of New Zealand sheep milk was different to that of milk from other countries
• If/how much the composition and flavour changed throughout the milking season
• How much the composition varied between different New Zealand producers
• If the composition and flavour changed upon processing and storage, and if so, how?

This project looks to:

• Determine the effect of processing on nutritional profile, compositional targets and product characteristics.
• Characterise compositional targets at an individual level, including effect of breed, lactation stage, age, seasonality, farm of origin and farm practice effects.

We investigated the following attributes:

This collaborative project collected milk from all our industry partners.

The research found:

• NZ sheep milk generally contains more protein (notably leucine, valine and isoleucine) fat (especially beneficial lipids such as medium-chain triacylglycerols and polyunsaturated fatty acids and phospholipids), carbohydrates, minerals (e.g. Calcium, Potassium and Magnesium) and certain vitamins than New Zealand cows’ milk.
• Microbial analysis demonstrated that our harvesting and storage protocols in New Zealand are providing a safe product for consumers.
• Sheep milk pH remained stable for nine days when stored at 2 or 4⁰C. Using the lower temperature prolonged storage by up to four days. However, storing at 2⁰C is preferable to retain high-quality protein and heat stability.
• Spray drying at low temperatures produces a product more desirable for reconstitution for drinking.
• Pasteurisation can be done quickly at temperatures of 75⁰C, though sheep milk may need to be diluted achieve this.
• Sheep milk powder had lower levels of the compounds associated with strong flavor (volatile fatty acids) and lower odour activity values compared to goat milk powder, suggesting a milder flavour of sheep compared to goat milk. Higher amounts of volatile fatty acids were measured in the spring (start of the lactation season) compared to autumn (end of the season) which may be due to variation in the composition of the pasture between early and late season.